But Luo, chair of the University at Buffalo’s physics
department, knows all about the secrets of pouring a smooth brew.
That’s because it’s just basic physics.

“You see so many things in everyday life that seem simple,
but if you look at the physics more closely, it’s really
quite neat,” he said. “There’s science
everywhere.”

So as fall gets underway and tailgating parties abound, drink
safely and take note: Cans with significantly wider mouths or two
holes — which some brands are newly marketing — really
do cut down on foam and awkward glugging, Luo says. It’s not
just an advertising gimmick.

Though most people know this intuitively, they may not be
knowledgeable about the science behind why this happens.

Allow Luo to fill you in.

The first concept to understand is atmospheric pressure. In a
nutshell, the atmosphere of the Earth — all the air molecules
floating around us — exerts a force that pushes on
objects.

To demonstrate how this works, Luo sometimes shows his classes a
simple experiment: He fills a mug to the brim with water, caps it
with a smooth glass plate, holds the pieces tight, flips the whole
contraption upside down and lets go. The water will stay in the
mug. Why? The pressure that the atmosphere exerts is enough to keep
the plate pushed up against the water.

“Atmospheric pressure is quite strong,” says Luo,
who teaches an undergraduate seminar titled, “Who Needs
Physics in the Real World?” “It’s enough to hold
10 meters worth of water. You don’t feel it because your body
is used to the pressure, but it’s there.”

What does this have to do with drinking beer?

As liquid exits a can, it leaves behind a vacuum — a
totally empty space in which you won’t find anything, not
even air molecules.

“Once you create this vacuum, the atmospheric pressure is
going to push air in,” Luo says. “It’s a dramatic
effect: Each time you drink, you create a small vacuum, and the
atmosphere responds by pushing air in.” (This is the same,
simple principal many modern pumps rely on: They push air out of a
space, creating a vacuum that air or water rush to fill.)

A super-wide hole or a second hole placed some distance away
from the first enables this pressure equalization to occur without
obstructing the beer leaving the can, Luo says.

As such, when it comes to getting an unbubbly pour,
today’s single-hole, pop-top beer cans may be inferior to
old-time counterparts like those seen on the hit show Mad Men,
which required revelers to punch a hole on each side of a smooth
lid — one for drinking, the other for taking in air. Luo
hasn’t seen Mad Men (he’s more of a fan of the Big Bang
Theory, a show that features physicists prominently), but he says
the old-fashioned beer cans sound like winners.

One last important question: What would happen if you drank beer
in a vacuum?

Nothing much, Luo says. The mini-vacuum drinkers create by
sipping on beer would just stay inside the can.

But worries about beer would probably be the least of your
concerns in such a situation, Luo adds.

“If you’ve ever seen the movie Total Recall, Arnold
Schwarzenegger dreams he landed on a planet where there was no air,
and his eyeballs came out,” Luo says. “That may not
actually happen, but your body may swell.”

“Here on Earth, you don’t feel the atmospheric
pressure because our bodies have an inside pressure that’s
the same as the outside,” he says. “But when you
suddenly put someone in a vacuum, that inside pressure is still
there, but the outside pressure is gone.”

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